1. Field of the Invention
The present invention relates to a package substrate used for a package for an electronic component, and more particularly, to a package substrate having an internal circuit and a structure in which a plurality of independent electronic components electrically connected to the internal circuit are included.
2. Description of the Related Art
Recently, cellular phones and personal computers use MPUs having increased clock frequencies. Thus, noise having many harmonics is likely to be superimposed in power supply lines for the MPUs.
In order to prevent the above adverse effect caused by the noise, typically a decoupling capacitor is often connected between a power supply line and a ground. The decoupling capacitor is a necessary element of a power supply circuit because the decoupling capacitor also suppresses a transient phenomenon of a power supply system.
In the related art, the decoupling capacitor is often surface-mounted on a package substrate to which an MPU is die-bonded. For example, a plurality of decoupling capacitors is mounted on the package substrate so as to surround the MPU. In such a structure, it is difficult to reduce the size of the package substrate.
For this reason, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-527908 discloses a structure in which a capacitor 101 is embedded in a package substrate 102 as shown in FIG. 18. Here, the package substrate 102 includes layers of a synthetic resin, such as an epoxy resin, and conductive layers that are laminated by a build-up method, and includes a space 102a therein. The capacitor 101 defined by a multilayer capacitor is embedded in the space 102a. On the package substrate 102, a die 103 is bonded via bumps 104.
The capacitor 101 used a decoupling capacitor is embedded in the package substrate 102 disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-527908. Thus, the area of the package substrate 102 can be reduced.
However, various problems arise in a structure in which an electronic component, such as a capacitor, is embedded in a package substrate. For example, an undesirable gap often occurs between the embedded electronic component and the package substrate, causing a decrease in reliability.
Further, when the location of the embedded electronic component is deviated from a desired position, there is the possibility of causing a poor connection of the electronic component to a via-hole electrode, in the package substrate, to which electronic components should be connected.